Analysis Of Transition Flow Characteristics In Hypersonic Inlet And The Effect Of Leading Edge Bluntness

The achievement of hypersonic vehicles requires advanced air-breathing propulsion systems.An inlet,as an important component of a hypersonic propulsion system,its complex flow transitions need to be accurately predicted and studied and analyzed to guide engineering applications.The research object of this study is a hypersonic inlet with a curved surface compression section.Research and analysis are carried out to meet the objectives of accurate calculation of flow field and accurate prediction of flow transition in hypersonic inlet.Firstly,the HLLC,AUSM+,AUSMPW and AUSMPW+schemes are implemented based on the open-source software Open FOAM platform,and the reconstruction methods and limiter functions are studied and compared,and the local time stepping method is introduced to accelerate the convergence.These solvers are verified by cases of flow around the cylinder,hypersonic inlet and scramjet.The flow field structure and parameters are studied and analyzed,and compared with the experimental results.The AUSMPW+scheme is selected for the rest of the flow field calculations.Secondly,in order to accurately predict the flow transition in hypersonic inlet,the prediction ability of modifiedγ-Re_θttransition model for hypersonic flow transition was studied.At the same time,the implementedγtransition model is verified at low speed and the correction method is explored.The results show that the modified transition model improves the prediction ability of the hypersonic transition onset location and the transition length.The implementedγtransition model can accurately predict the flow transition process in the low-speed flat plate case,and it is feasible to apply it to the hypersonic flow transition prediction after correction.The relevant transition model and its modified model are implemented based on Open FOAM,which lays a foundation for the accurate prediction of flow transition in the hypersonic inlet.Thirdly,the fully validated numerical scheme and the modified transition model are used to simulate the flow transition characteristics of hypersonic inlet.The effects of wall temperature on the flow field structure and parameters of the hypersonic inlet with laminar,transitional and turbulence states are studied,and the changes of shock-induced separation zone and thermal boundary layer near the inlet wall were deeply discussed.The results show that when the wall temperature conditions are the same,there are obvious differences in the flow field structure and parameters of the hypersonic inlet with laminar,transitional and turbulence states.It is necessary to consider the effect of flow transition in the numerical simulation of hypersonic inlet.The influence of wall temperature on the flow field structure and parameters of the hypersonic inlet is clearly,and the change law of flow transition in the hypersonic inlet with transition state is summarized.Finally,based on the above,the numerical simulation of flow transition characteristics of hypersonic inlet with leading edge bluntness is further carried out to deeply study the effects of the bluntness radius of the leading edge of the top plate（R_N）on the transition of the hypersonic inlet with isothermal and adiabatic wall boundary conditions.The results show that the effect of leading edge bluntness on the flow field structure and parameters of the hypersonic inlet is significant,and the effect of R_Non the flow field transition characteristics is summarized.This demonstrates the need to consider the effect of bluntness design on inlet flow transitions when designing hypersonic inlets for engineering purposes.